It was a final, devastating slap in the face for his parents, Faye and Mark, who will today finally bid farewell to the son they last saw in 2007.

A series of unprecedented events has sprawled over the subsequent decade — a murder acquittal, a coronial inquest, an historic deal to grant his boyfriend immunity from prosecution and the eleventh-hour discovery of his body.

The Harbour City is no stranger to sordid soap operas, but Matthew Leveson's disappearance had people talking.

His car was found abandoned at a park in the city's south. A Bunnings receipt for a mattock and duct tape, were in the boot.

The 20-year-old was last seen leaving ARC nightclub on the pulsating Oxford Street strip with his much-older boyfriend Michael Atkins in the early hours of Sunday, September 23, 2007.

His parents reported him missing two days later.

A murder trial

Mr Atkins stood trial for the murder and manslaughter of his boyfriend, and was acquitted by a jury in 2009.

Police tapes — where he denies the Bunnings purchases — were ruled inadmissible evidence, as police at the time had not informed him he was a suspect.

Mr Atkins exercised his right to silence during his trial, but was eventually grilled on what he knew about his boyfriend's disappearance at a later Coronial inquest.

Before he gave evidence he was issued a certificate under section 61 of the NSW Coroner's Act, which granted him immunity from prosecution for anything he said at the inquest.

The inquest began in 2008 but was suspended for the murder trial. It started again in 2015 — the first time in New South Wales history where a coronial inquest was held after a not guilty verdict was found in the criminal justice system.

Mr Atkins did not give evidence until 2016, almost 10 years after his boyfriend was last seen. In all, he faced five days of intense questioning.

A phone call from NSW Attorney-General Gabrielle Upton meant they were one step closer.

Ms Upton told the Levesons an unprecedented deal could be struck — Mr Atkins would be granted indemnity from prosecution for perjury and contempt of court for any evidence given at the inquest.

In return, he would lead police to Matthew's body. If nothing was found, there would be no deal.

Mark Leveson described the choice as "impossible". They decided to accept.

The wheels were in motion. Mr Atkins drew a map to a spot in the Royal National Park, south of Sydney.

In total police conducted 20 digs in several areas of the park, starting in November 2016.

But the process was not indefinite and by May 2017, time was running out.

After a five-day search, with only one hour left before time was to be called on the operation, police moved a small palm tree.

"They did that and I actually remarked to my wife 'that'd be a nice palm for home' just jokingly and within moments they put the palm down and that detective called over [Detective] Gary Jubelin," Mr Leveson said.

"Then Gary came across to us and said 'we've got him, we've found Matt' and it was just because they had moved that palm.

"We'd literally walked past this palm many times, literally one metre from Matt."

'We were a thorn in their sides'

Despite Mr Atkins leading police to the body, it did not mean he would be charged again with murder or manslaughter.

Double jeopardy laws, the section 61 certificate he was issued by the NSW deputy coroner and the separate deal struck with the NSW Attorney-General made this case unique.

Even if Mr Atkins' DNA was found on Matthew's remains — extremely unlikely after 10 years — all that would prove was that they were together in the lead-up to his death, something that had already been established in court and at the inquest.

"We would have loved both [prosecution and the recovery of remains]," Faye added.

"Atkins didn't matter. Our son was the most precious thing to us and to his brothers."

Matthew Leveson's family and friends gave emotional tributes at his funeral, which was held at Woronora Chapel in Sutherland today.

His best friend, Rachel Spanki, said Matthew touched the lives of many people.

"He had the most amazing huge and contagious smile, when he smiled it would just light up the room and you couldn't help but smile too, his personality just captured the entire room," she said.

"When I think about Matty the first thing that comes to mind is laughter and feeling happy, and all the wonderful times we had together."

Celebrant Boyd Duncan also paid tribute to the effort his family made to find Mr Leveson and lay him to rest.

"A family that has gone through so much and somehow come out the other side, a little battle weary but the battle was worth it because the battle has been won, the victory is theirs the trophy is their son, their brother, the boy who has now become everyone's Matty, " Mr Duncan said.

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